And began to speak with other tongues as the Spirit gave them utterance

On the Day of Pentecost, Jesus poured out His promised Spirit on all those gathered in the upper room in Jerusalem.

"And they were all filled with the Holy Ghost, and began to speak with other tongues [languages], as the Spirit gave them utterance." - Acts 2:4 KJV

Because it was Pentecost [Sukkot], there were Jews from all over the world celebrating this holy day.

"And there were dwelling at Jerusalem Jews, devout men, out of every nation under heaven." - Acts 2:5 KJV

It is only because God chose this holy day in which Jews from all over the world were present, that they realized this was the miraculous power of God. Otherwise, this great event of the outpouring of His Spirit would have been dismissed as nothing but a group of drunken Galilaeans.

"Now when this was noised abroad, the multitude came together, and were confounded, because that every man heard them speak in his own language. And they were all amazed and marvelled, saying one to another, Behold, are not all these which speak Galilaeans? And how hear we every man in our own tongue, wherein we were born? ...we do hear them speak in our tongues the wonderful works of God. And they were all amazed, and were in doubt, saying one to another, What meaneth this?  Others mocking said, These men are full of new wine." - Acts 2:6-8, 11-13 KJV

"But Peter, standing up with the eleven, lifted up his voice, and said unto them...these are not drunken, as ye suppose, seeing it is but the third hour of the day. But this is that which was spoken by the prophet Joel; And it shall come to pass in the last days, saith God, I will pour out of my Spirit upon all flesh…" - Acts 2:14-18 KJV

In what language was the Gospel preached on the day of Pentecost?

The Jews that were gathered in Jerusalem that day not only knew their native language from the country they were from, but as religious Jews, they also knew the Hebrew language. As members of the Roman Empire, they probably knew Greek and Latin as well, as these seem to have been the universal languages at that time.

Because all those that were gathered were religious Jews, it is most likely he was preaching in the Hebrew language.

The gospel message on the day of Pentecost was preached by Peter, not by the hundred and twenty speaking in tongues. The Bible clearly records the preaching that day, and it was by Peter. (Acts 2:14-40)

“But Peter, standing up with the eleven, lifted up his voice, and said unto them, Ye men of Judaea, and all ye that dwell at Jerusalem, be this known unto you, and hearken to my words:” – Acts 2:14 KJV

To be continued…